As a conventional radiation tomographic image generating apparatus, there is an X-ray tomographic apparatus, for example. This X-ray tomographic apparatus, as shown in FIG. 7, has an X-ray tube 101 and an X-ray detector 102 which are arranged opposite each other across an inspection object M, and are interlocked such that, synchronously with parallel translation of the X-ray tube 101 along the direction of body axis z which is the longitudinal direction of the inspection object M, the X-ray detector 102 moves parallel in a direction opposite to the parallel translation of the X-ray tube 101. Radiography is conducted continuously, while changing the X-ray emission angle of the X-ray tube 101 to the inspection object M, so that an arbitrary point on a particular sectional plane (reference plane) of the inspection object M will always be in the same position on the X-ray detector 102. With the X-ray tomographic apparatus, apart from such parallel translation (linear scan), various scanning tracks are realized, such as arcuate movement (circular scan) accompanying rotation (about an axis in a shorter direction perpendicular to the body axis z and a horizontal plane) of a C-arm (not shown) holding the X-ray tube 101 and X-ray detector 102 as shown in FIG. 8.
The X-ray tomographic apparatus is also called “Tomosynthesis”. To generate tomographic images with the tomographic X-ray apparatus, there are a reconstruction technique called “Shift Addition method” which carries out adding operations while shifting, each by a suitable amount, a plurality of projection data (radiological images) acquired by X-ray beams emitted from different directions (projection angles) to an inspection object, and a reconstruction technique called “Filtered Back Projection (FBP) method” (also called “Filter-Corrected Back Projection method”) as used in an X-ray CT (Computed Tomography) apparatus for generating tomographic images by revolving an X-ray tube and an X-ray detector about the body axis of an inspection object (see Nonpatent Document 1, for example).
Take a human body as an example of inspection object, there is a substance that forms the living body as the substance forming an area of interest in the inspection object. As substances of high density compared with this substance forming the living body, there are a metallic artificial joint, external fixator, dental stuffing, and so on. These substances of high density are formed of metal or the like, and the substances of high density compared with living body tissue absorb radiation. In addition, where substances of lower density compared with the substance forming the living body are included, the substances of low density compared with living body tissue transmit radiation.